THE ASCORBIC ACID CONTENT
OP SELECTED VEGETABLES DURING STAGES
0? PREPARATION AM SERVICE AT A COLLEGE CAFETERIA
SISTER FRANCIS HUGH ffALEKB, 0. S. U.
B. S. f Marymount College, 1933
submitted In partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE
Department of Food Economics and Nutrition
KANSAS STATE COLLEGE
OF AGRICULTURE AND APPLIED SCIENCE
I Alia03 674170
TABLE OP CONTESTS
REVIEW OP LITERATURE 3
SAMPLING PROCEDURE 26
CHEMICAL PROCEDURE 33
DISCUSSION OP RESULTS 36
LITERATURE CITED 47
Within recent years the increase in mass feeding has been
phenomenal. Institutional, commercial, and industrial con-
cerns as well as our Army and Navy have been the users of
large quantities of the nation's food supply. Numerous inves-
tigations are being made to ascertain the quality of food
served by the various types of eating establishments. The chal-
lenge that must be met by these establishments to a greater or
lesser extent is that of offering "short orders," of providing
some choice of selection, and of giving satisfactory service
involving quantity preparation.
Some of the culinary practices that prevail in large
quantity cooking undoubtedly cause much destruction of certain
nutritive values in food. Moreover, there Is no reason to
assume that the price the consumer pays for his food is an
index of the nutritive value of his diet, whether he chooses
his meals from expensive hotel dining rooms, coffee shops,
cafeterias, or from the lowest class restaurants.
The effect of preliminary preparation and methods of cook-
ing upon the nutritional value of foods has long been recog-
nized. In order to encourage the use of the best methods in
the preparation of foods for institutional service, it Is nec-
essary to know what standards should be set up. Since there
is essentially a vast difference between the problems found in
cooking in the home and in the commercial or industrial food
unit, many Investigations are needed on the nutritive values
of food as they are prepared for large quantity serving.
Recently some studies on Institutional service have been made.
The results that have been reported have Intensified the Inter-
est of those who are responsible for large group feeding.
The purpose of this thesis was to moke a study on an
Investigation carried out on selected vegetables In the cafe-
teria at Kansas State College where it was felt that In most
Instances the practices commonly used In Its kitchen prepara-
tion and counter service were very oomnendable. For example,
the use of a staggered time schedule would be expected to be
effective In conserving the nutritional values of foods. Cook-
ing vegetables In small quantities made It possible to hare
freshly cooked ones ready for serving as soon as the limited
supply previously taken to the counter had been depleted.
Suoh a plan eliminated the necessity of keeping some of the
cooked foods warm for an extended length of time on the stove
or steam table or In a bain marie. Also, a great deal of the
cooking was done In a pressure steamer, and the cooking peri-
ods of vegetables were not prolonged. Moreover, this cafete-
ria featured dishes using uncooked vegetables on the steam
table. There were other details of procedure that appeared to
contribute to the conservation of food values.
These were some of the reasons for choosing to ::take an
Investigation of the effects of certain preparations and
serving techniques on the ascorbic acid content of selected
vegetables at the college cafeteria.
That difficulties would be encountered In carrying out
this study ware recognized from the beginning. A cafeteria
kitchen does not readily lend Itself to scientific laboratory
experiments. Many variable factors have to be brought under
control In order to draw conclusions from data collected.
This Is especially true In the case of ascorbic acid studies.
However, In this work the student was so directed that she
could discover for herself the numerous problems Involved.
It Is hoped that further value con be derived from this
Investigation by maklne many applications of the Information
gained to the problems of the food service In her own Insti-
REVIEW OP LITERATURE
Determinations of the ascorbic acid content of the vari-
ous foods known to be the best and most common sources of this
vitamin have resulted in the accumulation of data that vary to
a remarkable extent. Sherman (194G) stated that a table of
single average figures would be unduly tentative and that in
most oases a rtnge of the values "within which it is reason-
able to expect that the mean values when settled will be
found" should have muoh more meaning.
There are many reasons to which the differences of the
original ascorbic acid content of fresh raw foods have been
attributed. Some of these are the horticultural selection
of seed, variety, locality, climate, soil, fertilizer, sea-
son, exposure to rainfall and sunshine, stage of maturity,
parts of the plant tested, conditions of harvest, handling,
storage, and methods of transportation. Many studies have
increased our knowledge of the importance of these factors
but further investigation is needed.
Somers, Hamner, and Nelson (1945) in order to determine
some of the factors that might affect the ascorbic acid con-
tent of tomatoes received at a cannery made a correlated
study of the several factors operating in a specific location.
They found that a certain uniform manner of processing toma-
toes did not result in marked changes of ascorbic acid values.
Therefore, the variation of the ascorbic acid content of can-
ned tomatoes must have been due to two sources: differences
in the ascorbic acid content of tomatoes in the field and
losses subsequent to picking and processing. These investi-
gators verified the findings of Hamner, Bernstein, and Maynard
(1945) who reported that the greatest influence of environ-
mental variables on the ascorbic acid content of tomatoes was
that due to variations in light Intensity two weeks previous
to harvest. Probably fluctuations hitherto attributed to
location or season at which tomatoes were produced were due
to the differences in amount of sunshine.
Wide differences in ascorbic acid content of tomatoes
have been found to occur within single varieties. Hallswork
and Lewis (1944) found a range of 24 to 51 mg. per 100 grams
in the same variety grown in the same plot.
Intervarietal differences would be expected to cause even
greater fluctuations. Currenoe (1940) showed that varietal
differences In the ascorbic add content of tomatoes were
difficult to demonstrate statistically. Reynard and Kanapaux
(1942) concluded from several reviews of literature that most
commercial varieties of tomatoes ranged from about 15 to 40 ng,
of ascorbic acid per 100 grams of fresh weight. However,
caution should be used in reoommending any one variety because
of variations to be expected under the wide range of condi-
tions where it might be grown. Of edible varieties tosted by
Reynard and Kanapaux, a small-fruited species gave an ascorblo
acid range of 35.3 to 72.6 mg. per 100 grams. Thirty commer-
cial varieties ranged from 11.2 to 21. C mg. per 100 grams.
Currence (1940) stated that emphasizing varietal differences
to the grower might be misleading since the variety recom-
mended as being of high vitamin C content might prove to be
low under some conditions. Murphy (1942) pointed out that
although variations within variety caused by geographical situ-
ation were comparatively large, this should not lessen the
importance of varietal values. She stated that tomatoes may
be rendered useless as a source of vitamin C if a variety of
low ascorbic acid content Is subjected to adverse environ-
mental Influences. Contrariwise, a high vitamin variety sub-
jected to the same unfavorable conditions could still contri-
bute materially to vitamin C requirements.
Brown and Mosor (1941) found that an 18-day storage per-
iod of tomatoes either at laboratory temperature or In the
refrigerator at 6.6° C. resulted in complete retention of
their asoorblo acid. However, Somers et al. (1945) suggested
that holding tomatoes more than a day, if they were Injured
and In a poor condition, might affect their ascorbic acid
The rate of destruction of ascorbic acid during cooking
varies greatly with different foods. Since this vitamin is
not autoxidlzable in an acid solution, and since tomatoes are
not ordinarily subjected to much manipulation a great loss of
ascorbic acid during cooking would not be expected. Much work
has been done to determine the effect of cooking upon the as-
corbic acid retention in some vegetables. Apparently few, if
any studies, have been made on the effect of cooking raw toma-
toes. This may be due to the fact that fresh tomatoes are
usually served raw and that when cooked tomatoes are wanted,
the canned ones are used. Such seems to be the case especially
Daum, Aimone, and Holllster (1943) reported the results
of a study on the ascorbic acid retentions in institutional
food service at University Hospital, Iowa City. Approximately
1400 persons were served in three groups ; therefore the vege-
tables were necessarily prepared in large quantities. The as-
corbic acid retention in canned tomatoes cooked for a period
of thirty minutes was 94.5 per cent. Holding the cooked, can-
ned tomatoes fifteen minutes on the steam table did not lessen
their ascorbic acid value. Cooking for thirty minutes and
holding for one hour on the steam table gave an 83.4 per cent
retention of the original ascorbic acid content of the canned
Somewhat different results were found by Hinman, Brush,
and Halliday (1944) who reported no effect on the retention of
the original ascorbic acid value of canned tomatoes durin a
boiling period of thirty minutes and subsequent holding period
of one and one-half hours on a steam table.
Gleim et al. (1946) reported that heating canned tomatoes
by various methods required for quantity preparation caused no
change in the retention of ascorbic acid when tomatoes were
heated to serving temperature. Simmering for thirty minutes
affected the retention slightly, and simmering for three hours
decreased the retention to 75 per cent.
Numerous investigations have been made on the ascorbic
acid value of cabbage. Murphy (1942) found that environmental
agencies, e.g., sunlight and rainfall and perhaps temperature,
had a marked influence on the ascorbic acid content of cabbage.
Evidence also indicated that the ascorbic acid tended to de-
crease as the tissues became more fully matured.
Others have reported wide ranges of ascorbic acid content
of cabbage due to varietal differences. Gould, Tressler, and
King (1936) found a range of 26 to 56 mg. per 100 grams in six
varieties and strains. They found that the same variety did
not have the same ascorbic acid content at different seasons
or in different years but that varieties high in ascorbic acid
yield as compared with other varieties tended to remain so from
year to year.
Van Duyne, Chase, and Simpson (1943) reported that the
storage of cabbage In tightly closed containers for two months
at a temperature of -0.5° to 4.0° C. gave good ascorbic acid
retentions. Losses did occur during the third month of stor-
age and when the stored cabbage was held subsequently at room
temperature, 19.4° C. for three days. Holding the cabbage for
a week in the refrigerator at a temperature of 2.0° to 2.5° C.
did not affect the retention. These findings seemed to corre-
late with the report of Mayfield and Richardson (1940) who
observed that a six-months' storage at 7.2° C. and a relative
humidity of about 55 per cent resulted in approximately 75 per
cent retention of the ascorbic acid value of cabbage.
Pyke (1942) performed an experiment to show the compara-
tive effects of various methods of shredding or mincing cab-
bage. He demonstrated that the less the injury to the tissue
oells, the greater the ascorbic acid retention. The use of
(1) a sharp knife which caused no noticeable bruising or dis-
coloration in shredding, (2) a household shredder which caused
more bruising than the above, and (3) a household grater which
caused considerable bruising and even discoloration of the cab-
bage gave results in harmony with theoretical considerations.
In (1) the asoorbic acid content was not lessened. A ninety
per cent retention was found in (2) and (3) showed a 66 per
cent retention. The greatest decrease in the ascorbic aoid
content in (2) and (3) occurred during the first five minutes
after the cabbage was shredded. After the initial changes, the
retentions did not vary significantly within a three-hour hold-
Lampltt et al. (1942) being interested also in finding a
correlation between mechanical breakage of cells and the reten-
tion of ascorbic acid, resorted to the expedient of testing the
liquid pressed out of shredded cabbage. They confirmed the
results of Pyke that the retention varied with the extent of
rupture of the cells and that the concentration of ascorbic
acid fell rapidly during the first ten to 15 minutes. The as-
corbic acid value remained oonstant for three-hour periods
when cabbage was held at 15° C.
Van Duyno, Chase, and Simpson (1943) reported that the
advance preparation of shredding cabbago and allowing it to
stand for one hour in air gave an ascorbic acid retention of
07 t 2 per cent. Allowing the shredded cabbage to stand In
water for one hour resulted in the retention of 94 ± 1 per cent,
and that held in water for three hours retained 96 ± 2 per cent.
MoCay, Pijoan, and Taubken (1944) reported that the use
of a plastic knife for cutting cabbage caused greater retention
of ascorbic acid during holding periods of the cabbage than
did the use of a steel knife or food chopper.
Qulnn et al. (1946) reported that cabbage that had stood
at room temperature for 20 minutes did not show a marked dif-
ference in ascorbic acid oontent whether the cabbage had been
prepared by shredding or by cutting with a knife.
Wellington and Tressler (1938) having reviewed various
reports concerning the ascorbic acid content of oooked cab-
bage found that great differences had been observed. They
made a comparison of three methods of cooking— boiling, steam-
ing, and panning. They concluded that the amount of aaoorblo
acid extraoted by the cooking water in boillne and in steaming
varied somewhat according to the more or less finely divided
oondltlon of the cabbage. About two-thirds of the original
ascorbic acid was retained in panning, and since there was no
excess liquid the oabbage itself retained the greatest amount
of vitamin C when cooked by this method.
Having made an investigation on the cooking of oabbage
by boiling, Gould, Tressler, and King (1036) pointed out that
the length of time required to bring the water to a boll after
the cabbage whs added seemed to be of significance. They found
that about 25 per cent of the ascorbic acid was destroyed be-
fore the cooking water began to boll and that very little was
lost thereafter, although a considerable amount was dissolved
In the cooking water.
Van Duyne, Chase, and Simpson (1943) reporting on the
effect of various home practloes on the ascorbic acid content
of oabbage, stated that when cabbage was boiled for seven min-
utes in the proportions of one part by weight of cabbage to
one-half, two, and four parts of water the percentage reten-
tions were, respectively, 70 ±2, SO $ 3, and 51 ± 1. They
made a study on the effect of boiling cabbage in twice its
weight of water for different lengths of time. The results
showed percentage retentions of ascorbic acid as follows:
after seven minutes, 55 x 2; after 15 minutes, 52 ± 1; after
25 minutes, 52 t 2. Having compared the effects of cooking
oabbage to the same degree of "doneness" by boiling (1) oov-
ered in twice its weight of water for seven minutes, (2) un-
covered in twice its weight of water for eight and one-half
minutes, and (3) uncovered In four times Its weight of water
for five and one-half minutes, they found these percentage
retentions of ascorbic acid: in (1), 56 ± 2; in (2), 50 ± 2;
and (3), 49 1 1.
Ireson and Eheart (1944) reported that using a large
amount of water, 1200 cc. to 240 grams of cabbage, resulted in
a 54 per cent retention of ascorbic acid. About 37 per cent
of the vitamin was extracted in the water and nearly nine per
cent was oxidized. When a smaller amount of water was used,
40 cc. to 193.7 grams of cabbage, the 16 per cent loss of as-
corbic acid was due to oxidation.
Noble and Waddell (1945) showed that cooking cabbage in
a tightly covered pan with just enough water to cover, or in a
steamer, or in a pressure saucepan, retained approximately the
same proportion of its original ascorbic acid. Cabbage coolced
in an open kettle with enough water to cover during all of
the cooking period retained much less than that cooked in the
steamer or pressure saucepan. In another study reported In
1946, these same workers found results comparable to those
Just mentioned. The retention of ascorbic acid in cabbage
cooked in a steamer and in a pressure saucepan averaged slightly
less than 70 per cent, whereas that of cabbage cooked by the
tightly covered pan method retained about 60 per cent and that
by the open kettle method retained about 35 per cent.
Higgins (1942) in a comparative study of institution and
home-cooked vegetables found that cabbage cooked in large
quantity was comparable in quality and ascorbic acid reten-
tion to that cooked according to ordinary home procedures.
Holding over steam for one hour affected the retention of as-
Daura, Almone, and Holllster (1943) reported a study on
large quantity cookery of cabbage. About 300 pounds of cab-
bage were usually cooked at one time, but excellent flavor
and color were retained. The range of ascorbic acid in the
raw cabbage in 12 determinations was found to be 21.0 to 26.0 .ug.
per 100 grams. After the cabbage was oooked the range was 12.0
to 19.0 nig. The percentage retentions of ascorbic acid in
cabbage in cooking, in holding 15 minutes on the steam table,
and one hour on the steam table were: 59.1, 54.6, and 45.5
per cent respectively.
Although extensive research has been carried out on pota-
toes, it is difficult to conclude to what extent they enrioh
the vitamin C content of our diet. The various factors which
influence the ascorbic acid value of potatoes have been inves-
tigated by many scientists. In some cases the work is being
Leichsenring (1944) made a compilation of data from the
agricultural experiment stations of Illinois, Nebraska, North
Dakota, and Minnesota. In reporting the studies made on
variety, she stated that marked varietal differences in the
ascorbic acid content of potatoes were found. The highest
and lowest values attributed to variety showed a difference
of 113 per cent. It was indicated thtt some varieties having
comparatively higher ascorbic acid values tended to have
approximately the sumo values from year to year.
Dove, Kurphy, and Akeloy (1943) also reported evidenoe
showing that potatoes of higher ascorbic acid value could prob-
ably be counted on to yield similar values from year to year.
IJdo (1937) found varietal dlfferancea up to 60 per cent
In the ascorbic acid content of potatoes and not more than a
ten per cent difference in tubers of the same variety.
Esselen et al. (1942) in a study on the effect of variety
found that in many cases differences between varieties were
less than differences within a singlo variety. They cave
13.1 nig. per 100 grans as an average yield of Irish Cobblor
and 9.7 mg. per 100 grams as an average of Chippewa potatoes.
These figures were based on the results of tests niado on pota-
toes from several statou.
Leichsanring (1944) said that although locality appeared
to be a factor of sorao importance In the ascorbic acid content
of potatoes, maturity and season seemed to be cor.conitant fac-
tors . Her data showed that the same varieties of potatoes
harvested during October, 1943, In Nebraska and North Dakota
had higher ascorbic acid values than those harvested in Minne-
sota during October, 1942. In these reports the Irish Cob-
bler variety was consistently the highest. Its ascorbic acid
values were these: In North Dakota, 27.1 mg. per 100 grams;
in two different places in Nebraska, 23. S mg. and 33.2 mg.;
and at three plaoes in Minnesota, 12.6, 16.4, and 19.0 mg.
Esselen et al. (1942), having made a study on potatoes
Immediately after they were dug at their own station in Massa-
chusetts and on those shipped "soon after harvest" from Cali-
fornia, Kentucky* Maine, and Hew York, did not attribute very
great importance to the effect of different geographical areas*
According to Leichsenrlng (1044) the investigations car-
ried out by the Nebraska station on five varieties of potatoes
showed marked and continuous decrease during the growing per-
iod as well as after harvesting and during storage. An ascor-
bic aoid content of 36,8 mg, per 100 grama of immature Irish
Cobbler potatoes was found on June 30, 1043. Weekly analyses
thereafter shov ed continuous decreases in ascorbic aoid con-
tent. At the time of harvest on August 10, 1943, a value of
23.8 ng. per 100 grems was found.
Reports concerning the distribution of ascorbic acid in
the potato tuber vary somewhat. Rolf (1940) found that the
concentration of ascorbic aoid was higher In the bud end than
in the stem end. Immature potatoes of the Chippewa variety
showed practically no difference in the distribution of ascor-
bic acid in the various sections of the tubers, although there
was. a slight tendency toward higher concentration In the bud
end as they reaohed maturity. New Green Mountain potatoes
bought on the market showed only a slight tendency to have a
higher aaoorbic acid content in the bud end than in tho stem
end when purchased. This difference became very apparent by
the end of a week and increasingly more pronounood thereafter.
The Leiohsenring data (1944) seemod to indicate that the as-
corbic aoid content of potatoes was greater at the apioal end
then at the stem end of the tuber*
IJdo (1938) reported that there was a uniform distribu-
tion of ascorbic acid throughout the potato, but Julen (1944)
found that the concentration of vitamin C was greater in the
layer nearest the peel than in the oore.
Esselen et al. (1942) found that in raw potatoes there
was an even distribution of ascorbic acid in the tuber itself
with a lesser amount in the skin. However, in boiled potatoes
there was a greater amount of aacorbio acid in the area be-
tween the central and epidermal portions. The skin and part
just beneath it were about equal in ascorbic acid content.
In baked potatoes the greatest concentration of ascorbic acid
was in the central portion with the amount decreasing pro-
gressively toward the skin. These workers concluded that some-
thing happened during cooking to change the distribution of
ascorbic acid in potatoes. They suggested that this effect
might be due to the higher temperature maintained in the
outer portions because of direct contact with the heating
medium. In the case of boiling some of the vitamin was leached
into the water. Rolf (1940) reported that she found a similar
distribution in cooked and uncooked potatoes; therefore there
was but little diffusion of the vitamin during cooking.
According to Leiohsenring (1944) the Minnesota station
found that the size of the tuber was not a significant factor
in the ascorbic acid content of potatoes. Esselen et al. (1942)
also reported that there was no correlation between the size
of tubers and their asoorbio acid content. They found marked
variations In both small and large nature ran potatoes.
Rolf (1040) pointed out that although a range of 1.5 mg,
to 53.0 mg. of ascorbic acid per 100 grams of potatoes had boon
reported by various workers, their investigations showed that
newly harvested potatoos were highest in ascorbic acid and that
this quantity diminished very rapidly during the first part of
storago and more gradually later. She stated that storage at
25.5° C. of immature Chippewa potatoes resulted in an 80 per
cent retention of ascorbic acid after one week and C4 per cent
after three weeks. Hew Green Mountain potatoes bought on the
market showed a retention of 86 per cent in about ten days at
25.5° C. She found that the ascorbic aoid value of three vari-
eties of potatoes stored at 15.5° C. decreased rapidly during
the first few weeks and then more gradually until at the end
of 26 weeks, the ascorbic aoid had nearly reached a plateau
value. A storage temperature of 4.5° C. caused a greater de-
crease. The Oreen Mountain variety stored at 15,5° C. lost
50 per cent in five months. This worker stated, hovvever, that
evidence seemed to lndioate that the detrimental effects of
storage at low temperature upon the asoorbic aoid content of
potatoes might be offset to some extent by later storage at a
All the station reports summarized by Leichsenring (1044)
indicated that during the storage of potatoes their asoorbic
aoid retentions were gradually and significantly decreased.
A storage temperature of 10,0° C. seemed to be more favorable
for ascorbio acid retention than 4.4° C. In Nebraska Triumph
potatoes harvested in August and stored at 10,0° 0. shoved
ascorbic acid values of 16.5 mg. per 100 grass in Deoember and
7.9 mg. in April. Those stored at 4.4° C. had an ascorbic
add value of 5.3 qg« in Deoember and 5.2 rag. in April.
Other studies on the effeot of temperature and length of
storage correlate rather closely with the data given above.
Esselen et al. (1042) observing the effect of storage repor-
ted that two varieties held five months at 2.2° C, approxi-
mately the temperature of oold storage, had a higher asoorbic
acid value than the same varieties held at 4.4° to 10.0° C,
similar to the temperature of dry 'underground storage? but
four varieties hud greater ascorbic acid value after being
stored for five months at the higher temperature. Storage
seemed to level off the differences between varieties in ascor-
bic acid content.
At the University of Wyoming Agrioulturo Experiment Sta-
tion (1040-1941) it was found that the ascorbic acid retention
in potatoes ranged from 43 to 60 per cent during the four-
month storage period between Deoember and May. The temperature
of the storage was not given.
Julen (1944) of Sweden reported that potatoes stored
Indoors at 18,0° to 20,0° C. retained more vitamin C than
those stored at 2,0° to 3.0° C.
Lelohsenring (1944) noted that the differences in the
asoorbic add retentions of potatoes during cooking were attri-
butable to suoh factors as amount of water used, sire of potato
pieces, length of cooking time, method of cooking, and manner
of sampling. The Illinois station reported the following per-
centage retentions of ascorbic acid in potatoes during cooking:
after baking, 87; boiling in skins, 103; peeling and steaming,
86; peeling and boiling, 85; peeling, halving, and cooking in
the pressure cooker, 85. Work at the Nebraska station showed
that allowing cooked potatoes to stand for 15 minutes before
analysis decreased the retention of ascorbic acid.
Rolf (1940) found that the boiling and steaming of unpared
potatoes were the cooking methods least destructive of vitamin C.
Baking and pressure cooking caused slightly decreased retentions
while boiling pared potatoes affected the retention to a greater
extent. The ascorbic acid retention In any of these methods
was not less than 75 per cent.
Esselen et al. (1942) found that in eight varieties of
potatoes there was a smaller average retention of ascorbic
acid in baking than in boiling the whole potatoes in the skin.
These workers made the observation that the addition of one
per cent UaCl to the cooking water of potatoes seemed to aid
in the retention of ascorbic acid. They reported that boiling
In the skin, baking and French frying appeared to be the beat
methods of cooking potatoes from the standpoint of ascorbic
acid retention. The percentage retentions after cooking by
various methods ranged from 20 to 67. The procedures of peel-
ing, cutting in half, and slicing of raw potatoes, and the
mashing of potatoes, in the order named, caused increasing
losses of ascorbic acid. Potatoes boiled and then fried re-
tained 21 per cent of their original ascorbic acid value.
At the University of Wyoming Agricultural Experiment
Station it was reported that one-third of the ascorbic acid
of potatoes wus extracted by the water in which they were
Richardson and Mayfield (1943) found that boilinc unpared
potatoes caused no significant effect on their ascorbic acid
retention. Cut, pared potatoes retained approximately 01 per
oent after boiling. They reported that cooking pared potatoes
in a pressure saucepan under steam pressure of 15 pounds gave
better retention of ascorbic add than did boiling in an ordi-
Recently there have been studies on the ascorblo acid
content of potatoes as affected by Institutional methods of
preparation and service.
Higgins (1942) found that the retention of ascorbic acid
of potatoes cooked by Institutional methods was slgnifioantly
less than of those cooked by home methods.
Kahn and Halliday (1944) reported a study on the vitamin
values in foods prepared in institutional quantities. Steam-
ing in tho skin was the only method of preparation which did
not affect the retention of aBOorblc acid in potatoes. Hew
potatoes, steamed in the skin, oan take the place of a citrus
fruit as a source of ascorbic acid. French-frlod potatoes
showed good retentions of asoorblo acid when the temperature
of the frying fat was kept oonstant. Baked potatoes retained
80 per cent of their asoorbio acid during baking. The reten-
tion was decreased to 50 per cent after a 43-mlnute holding
period on the steam table. A 61 per cent retention of the
ascorbic acid value was found as the rosult of cooking and
mashing potatoes. The average retention of the noshed pota-
toes after being held for 75 minutes was five per cent of the
Daum, Airaone, and Holllster (1943) reported that both
new and old potatoes showed slightly decreased values of ascor-
bic acid after cooking. A 15-mlnute holding period affected
the retention and holding one hour greatly decreased the re-
Stroightoff et al. (1946) undertook a study to determine
the effeot on the ascorbic acid content of potatoes of large-
scale methods of preparation such as those practiced in the
army consolidated mess and company raess. They reported evi-
dence to show that holding peeled raw potatoes covered with
water in a refrigerator overnight, or as long as 22 hours, or
in running water for four hours, did not groatly affect the
retention of ascorbic acid. This la a point of significance
because holding potatoes In water is a practice frequently
resorted to, eapoclally In Institutions, Richardson and Kay-
field (1943) found that the presoaklng of pared potatoes In
water for four hours decreased the subsequent retention of
aaoorbio acid in boiling or pressure cooking by about four
per cent. Soaking for four hours in 2.5 per cent salt solu-
tion before cooking resulted in better retention of vitamin C
than ocourred when potatoes were cooked at onco after prepara-
Strelghtoff et al. (1946) found that cooking potatoes In
the pressure steamer wus most conservative of the aaoorbio
acid value. The retention In this case was about 04 per cent.
Baking In tne Jackets a minimum length of time and boiling
gave percentage retentions of 88 and 87. When steamed pota-
toes were mashed, there was very little retention of ascorbic
Jenkins (1943) reported that cooked whole potatoes held
at room temperature retained more ascorbic acid than mashed
potatoes. Whether the potatoes were kept hot in small por-
tions or large quantities did not seem to affect the retention.
Keeping mashed potatoes warm for one hour gave a 25 per cent
retention of ascorbic acid. The length of time consumed in
the mashing of potatoes was a factor In ascorbic acid retention.
Cutlar et al. (1944) in making a review of literature
reported various ascorbic acid values for spinach. The amounts
ranged from 19.8 to 123.9 mg. per 100 grams. Tressler, Mack,
and King (1936) found that variety was an Important factor in
the ascorbic acid content of spinach. Broad Flanders yielded
an ascorbic acid value of 89.0 mg. per 100 grams and Princess
Juliana had the lowest value, 38.0 mg. per 100 grams. They
also reported that soil and growing conditions exerted a def-
inite influence on the ascorbic acid content of spinach.
Twelve varieties of spinach grown on upland clay loam soil
averaged 50 per cent higher than those grown on muck soil.
Spinach grown in the autumn had higher ascorbic acid values
than that grown in the spring. Isgur and Fellers (1938) in
a study on the effeot of fertilizer on Sew Zealand spinach
found that high nitrogen treatments did not increase the as-
corbic acid value.
Slepykh (1940) reported thct the ascorbic acid of the
spinach leaf reached its maximum content during the middle
stage of development and decreased with the maturity of the
plant. Sheets et al. (1941) found that the ascorbic acid
value of splnaoh was more concentrated in the leaf blades than
in the petioles. Trossler, Hack, and Xing (1936) gave data
to show that the ascorbic acid in splnaoh is principally in
the leaves and that the stems are almost devoid of this vitamin.
Tresaler, Mack, and King (1936) reported that splnaoh
stored for three days at 1.0° to 3.0° C. retained nearly all
its vitamin C, but that held at room temperature lost approxi-
mately one-half its ascorbic add value in three days and
almost all in seven days. Wheeler and Tressler (1939) found
that freshly harvested New Zealand spinach had an ascorbic
acid content of 44.0 mg. per 100 grams. After storage at
room temperature for four days the value decreased to 21 mg.
and storage of the fresh spinach for two weeks at 1.0° to
3.0° C. decreased the value to 16.0 mg. per 100 grams. Ran-
ganathan (1936) tested the effect of storage at room tempera-
ture on samples of fresh spinach collected during dry weather
and of spinach collected during wet weather. The initial
ascorbic acid oontents were 36.9 and 53.3 rag. per 100 grams,
respectively. After 24 hours the percentage retention of
ascorbic acid in the dry weather splnaoh was 70.0 and after
192 hours, 21.7. The wet weather spinach showed retentions
of 87.1 and 59.3 per cent, respectively, for the two storage
Procter and Greenlie (1930) reported that oven for short-
time storage of spinach, temperatures below 4.4° C, tended to
conserve vitamin C which deteriorated rapidly at ordinary room
temperatures, '/epplin and Elvehjen (1944) tested spinaoh soon
after harvesting that had a high original ascorbic acid oontent
of 79 to 90 rag. per 100 grams. The retention decreased rapidly
during storage at room temperature for 24 to 48 hours but was
more stable thereafter. Refrigerator storage offered acme
protection and after 72 hours the retention was slightly more
than 50 per oent. When spinaoh was exposed to room tempera-
ture again, the oxidation proceeded at a high rate.
Platenius and Jones (1944) said that spinaoh held in an
atmosphere of low oxygen oontent retained more than three
times as muoh asoorbio acid as the lots in normal air. The
presence of 18 per oent CO2 at a temperature of 66.0° F.
accelerated the destruction of ascorbic acid but 5.3 per oent
CO2 at 50.0° P. slightly retarded the loss of asoorbic acid.
Halliday and Eoble (1936) having made a comparison of
the asoorbio aoid retention during oooklng of a number of
vegetables, found that spinaoh retained the least amount, 24
per oent, during boiling for eight to nine minutes in a large
amount of water, i.e., 2f C. to 370 grams of spinaoh. Of the
76 per oent loss, 47 per cent was totally destroyed and 29 per
cent was dissolved in the oooklng water. When cooked in only
the water clinging to the leaves, approximately 36 per cent
was retained. Of the amount lost about 45 per cent was des-
troyed and 19 per cent was dissolved in the cooking water.
Dunker and Fellers (1930) made a study on the effect of the
amount of water used in oooking spinach. The retention of
ascorbic acid in spinach decreased as the volume of cooking
water increased. The solid portion retained a range of 32 to
67 per cent depending on the amount of water used. One pound
of spinach steamed with 100 cc, of water retained about 68 per
cent. One pound of spinach cooked with 450 cc. of water re-
tained about 33 per cent. Ten to 15 per cent of the ascorbio
acid was leached out into the liquid during steaming and dur-
ing cooking with the larger amount of water.
Phillips, Dickorson, and Penton (date of the report was
not given) found that cooking 600 grans of spinach with no
more water than that which clung to the leaves gave an ascor-
bic acid retention of 60 per cent. The oooking time required
was 12 minutos. Cooking the same amount of splnaoh In 250
grams of water and in 626 grams of water for six minutes gave
retentions of 55 and 41 per cent respectively. They found
that oooking 600 grams of spinach in 625 grams of water at an
initial temperature of 90,5° C, gave a 41 per cent retention
of ascorbic acid. The sane amount of spinach in the same
amount of water at an initial temperature of 20.0° C. gave a
34 per cent retention. The cooking times required were six
minutes when the initial temperature was higher and 15 minutes
when it was lover.
Cutlar et al. (1944) reported that in quantity oooking
the retention of the ascorbic acid of spinach was increased
by ten percent when the amount of water was Increased four
times above the amount required to cover the spinach as it
began to cook In steam- jacketed kettles. Spinach, in 15-
pound lots, boiled In otoam-Jackoted kettles with eight quarts
of water retainod 50 per oont of tho original asoorbio acid
but only 40 per cent when four times as much water was used.
The same amounts of splnaoh cooked in a container on tcp of
the range with eight quarts and two quarts of water retained,
respectively, 32 and 33 per cent of the ascorbic acid. These
workers observed that when the smaller amount of water was
used, more time was required for the spinach to reach a stage
of "doneness" than that cooked in the larger amount of water.
The length of time required for the water to reach the boiling
point after the spinach was added depended on the amount of
water and the concentration of heat on the bottom and sides
of the cooking utensil. Increasing the quantities of spinach
cooked at one time decreased the ascorbic acid content. Spin-
ach in five-pound lots cooked in the pressure steamer, stecaa-
Jccketed kettle, and In a stockpot on the range had decreasing
amounts of ascorbic acid according to the order of equipment
named. The retentions for the pressure steamer were 76 per
cent; for the steam-Jacketed kettle, 67 per cent; and for the
stockpot on the range, 53 per oent. Splnaoh In 15-pound lots
cooked in a 25-gallon steam-Jacketed kettle gave a retention
of 50 per cent. The same amount cooked in the same amount of
water in a 16-gallon stockpot on the r ange gave a retention of
32 per cent.
Cutlar at al. (1944) also i'ound that drained cooked
spinach held at 150° P. in a heated food service unit retained
85 per cent of its ascorbic acid after 15 minutes, 61 par cent
aftor 30 minutes, and 25 per cent after 120 minutes.
Since the purpose of this study was to make comparative
determinations of the ascorbic acid content of selected vege-
tables during stages of preparation and service, it was found
advisable to take samples as representative as possible from
the lots of vegetables as they were ordinarily prepared by the
regular workers of the cafeteria. Thus no effort was made to
determine the highest possible original content in any case.
Samples were also tested to determine the effects of 15-ralnuto
holding periods on the stean table because during ordinary
serving periods 15 minutes was the longest time any food was
held on the steam table before it was served and the dish
replenished by a new supply from the kitchen. At the cafeteria
all the samples of the vegetables to be tested were collected
into previously prepared bottles of metaphosphoric acid, taken
to the laboratory, and there analyzed at once for their ascor-
bic acid content.
In order to become familar with kitchen procedures and
details of the problems involved in this study, small numbers
of samples were taken over a period of several days, first of
tomatoes and then of cabbage. Later a larger group of samples
of each of the vegetables were taken for more extensive study.
At the cafeteria work was usually started on tomatoes
about 10:30 a.m. when they were taken from the refrigerator,
weighed, washed, oored and quartered. Then they were sent to
For sampling, tomatoes were selected that were free from
blemish and of uniform ripeness as Indicated by color and
firmness. For the analyses of raw tomatoes each of four washed,
cored tomatoes was cut into quarters. One quarter of each of
the tomatoes was put into each of four bottles of acid. For
analyses of cooked tomatoes, a whole raw tomato, washed and cored,
was weighed and put into each of six individual baking
dishes. The small porcelain dishes were used in order to keep
the weighed tomatoes separate. These dishes of tomatoes were
placed in a shallow stainless steel pan, covered with a damp
cloth and held at kitchen temperature until the tomatoes to
be served on the steam table were cooked. Then three of the
dishes were plt.ced in the steamer or oven at the same time and
for the same length of time as were the tomatoes to be served
first. The remaining three dishes were held for a longer
period at kitchen temperature and then cooked as above. After
the samples were cooked, they were transferred into bottles
of acid. Approximately 50 samples of tomatoes were thus stud-
ied over a period of five days.
For a larger number of samples, four tomatoes were cut
into fifths. One-fifth was placed into each of five bottles
of acid which had been previously weighed. Another four toma-
toes were cut into fifths and put into each of five baking
dishes and the procedure was repeated using bottles or baking
dishes until the following samples were collected: ten for
testing tomatoes raw, ten for testing tomatoes after they had
been steamed for five minutes, and ten for testing tomatoes
steamed five minutes and held on the ste ■ m table for 15 minutes.
Over a period of five days 39 samples of cabbage were
analyzed for their ascorbic ucid content. The preliminary work
on the cabbage was usually begun about 10:00 a.m. in a basement
room of the cafeteria and oontlnued until the cabbage was ready
for cooking. Approximately 15 pounds of cabbage were cleaned,
washed, quartered, cored and sent to the kitchen where the
cabbage was shredded on an electric Hobart slicer. The shred-
ded cabbage was put into a large stainless steel pan 20" x 19°
x 4", covered with a well dampened cloth and allowed to stand
until it was ccoked. Generally there was a standing period of
30 to 45 minutes in the kitchen before the cabbage to be served
first on the counter was placed in the steamer.
In order to ;et random sampling, the cabbage as soon as
it was shredded, was well mixed with forks, and samples were
taken for chemical analysis. Approximately two-ounce portions
were weighed and put into each of three bottles of acid which
had been prepared for this purpose. In all instances great
oare was taken to have the samples well oovered with aold.
lasaediately preparation for taking samples of cabbage for
steaming was begun. About one pound of shredded cabbage was
plaoed in a small stainless steel pan. Fifty-gran portions
were welgnad Into each of six porcelain baking dishes which
were placed in a large shallow stainless steel pan, covered
with • damp oloth and allowed to remain in the kitchen until
the cabbage that was to be served first on the counter was
cooked. This cabbage for serving on the counter Hsi the sam-
ples for testing for ascorbic acid content were plaoed in the
steamer at the same time and for the some length cf time.
When the cabbage was taken from the steamer, three of the sam-
ples were put into aold. Three of the oabbage samples, as
soon as they htd been removed from the steamer, were placed
on the steam table for IS minutes during a regular serving
period when the steam was turned on as usual, and then collected
into 6.cid. The baking dishes did not cool rapidly, but It was
deolded they were the best small containers for this purpose.
The retention of heat might have been somewhat similar to that
in a larger quantity of vegetable.
Samples were also taken from the large quantity of raw
shredded cabbage after it had stood at kitchen temperature
for 45 to 60 minutes.
When a larger number (40) of samples were taken, about
six pounds of oabbage, cleaned, washed, and shredded, were
placed in a stainless steel pan. l*rora this three sets of sam-
ples were taken alternately, i.e., as oabbage was weighed, one
portion was put into acid, the next portion into a baking dish
for steaming, and the third portion into a baking dish for
steaming and holding 15 minutes on the steam table. This was
repeated until there were ten samples in each lot. After
being steamed ten samples were collected into acid at once and
ten were placed on the steam table for 15 minutes. The steam
table was heated the same as it was during a regular serving
period. The remainder of the raw cabbage was left in a large
stainless steel bowl for one hour. It was then mixed with
forks and ten weighed samples were put Into acid.
Exploratory work was done on ten samples of potatoes.
The samples were taken from the potatoes that were being pre-
pared for serving on the counter. About 20 pounds of potatoes
had been washed, peeled in a Hobart machine, eyed by hand, cut
into quarters, and allowed to stand in water at room tempera-
ture. Usually the preparation was begun about 8:30 a.m. and
finished between 9:30 and 10:00 when the potatoes were sent
to the kitchen. Thus some of the potatoes were in water for
a longer period of time than others. An attempt was mude to
take random samples by selecting potatoes from different parts
of the container.
Raw potatoes were weighed In 50-gram portions and put into
four bottles of acid. For samples of cooked potatoes 50 crams
of raw potatoes were placed In each of four cheesecloth bags
and Inserted in various parts of the perforated steamer pan
among the potatoes being prepared for the counter, and steamed
for 30 minutes. These cooked samples were weighed and put
Into acid. The average loss of weight was found to bo 1.4
grams per 50 grama of potatoes. Therofore, It was assumed
that 48. 6 grams of cooked potatoes were equivalent to 50 grama
when raw. Accordingly four 4G. 6-gram portions were taken from
the potatoes mashed in the Hobart mixer after four minutes of
mashing before the addition of milk. This was not representa-
tive procedure sinoe the mashed potatoes for serving were
ordinarily subjeoted to mixing and whipping for a much longer
It was decided to uae a dry weight baaia for comparison
of ascorbic aoid values of potatoes when making observations
on a largor number (40) of samples. It was felt that this
method would be more accurate than that of assuming that 1*4
grams represented the loss in weight per 50 grams of potatoes
aa was done in the exploratory work.
For thla aet of samples ten 50-gram portion* of raw pota-
toes were weighed and put Into aoid. Ten samples taken from
the lot of potatoes that had been steanod 35 minutes were put
into acid. Ten samples of the mashed potatoes ready for serv-
ing were collected into acid. About 600 grama of the mashed
potatoes for serving were placed in a atalnleas ateel bowl
and allowed to stand on the baok of the kitchen atove for 45
minutes. Fifty-gram amounts were put Into each of ten bottles
For calculating the percentage of dry weight a little more
than 60 grama of potatoes from each lot from which samplos
had been taken. I.e., raw, steamed 35 minutes, mashed, mashed
and held 45 minutes, were put Into wide-mouthed, pint-size,
Kerr canning Jure which were then tightly sealed and taken to
the laboratory. Twenty s;rams of each were put Into each of
three aluminum drying dishes which had been previously prepared
and weighed. These samples wore dried in a Preas vacuum oven
at 100° C. and 18 pounds pressure for 18 hours. They were
weighed and the percentage of dry weight of the various lots
of potatoes from which they were taken was determined.
In order to obtain a number of samples of spinach large
enough to be indicative of results, ten samples were collected
during various stages of preparation of the spinach. The first
samples were taken from the spinach as it was delivered, unwashed.
Fifty-gram portions were weighed and put into acid. The rest
of the spinach was washed three times and the long stems were
removed so t hat s»bout one inch of stem was left. The spinach
was dried by being spread out on tea towels and paper toweling
and patted dry with paper and cloth towels. It was placed on
a board and cut with a French knife as was ordinarily done for
the serving of raw spinach on the steam table. Twenty 50-gram
portions of this spinach were collected alternately into acid
and Into baking dishes. The ten baking dishes of spinach were
held for 15 minutes on the steam table which was heated as for
ordinary serving, and then the samples were put Into acid.
The remainder of the raw, washed, and cut spinach was
held in a large stainless steel bowl at room temperature for
one hour. Ten 50-gram sanpleB were then put into the acid.
The indophenol titration method of Bessey and King (1933),
modified by Mack and Treasler (1937), as described by Bessey
(1939) was used in analyzing samples for their ascorbic acid
To prepare a 0.05 per cent solution of sodium, 2,6-dichlo-
rophenollndophenol, the indicator or dye used, 125 mg. of
Indophenol (Eastman) was r j.aced on a filter paper and washed
into a volumetric flask with hot water. After cooling, the
volume was made up to 250 cc. The aqueous solution of the dye
changes slowly ever, at low temperature; hence It was kept in
the refrigerator and fresh solutions were made not less fre-
quently than every four dayB. The dye was 3tar.darized against
ascorbic acid each day it was used.
The ascorbic acid solution for the standardization of the
dye wss carefully prepared by dissolving one ampule (0.1 gm. )
of crystalline ascorbic acid (Cebione Merck) in three per cent
metaphosphoric acid and bringing the volume up to 200 cc.
To standardize the dye, five cc. of ascorbic acid solution
were diluted with a small amount of distilled water and titrated
with dye until a very faint pink color persisted for 30 seconds.
The strength of the ascorbic acid solution was checked by
titrating a five-cc. portion, to which a arriall amount of sodium
bioarbonate had been, added, with 0.011? iodine until the end
point was almost reached. Then two drops of starch solution
were added to the ascorbic acid solution and titration con-
tinued by drops until a blue oolor first appeared. The iodine
solution was prepared by taking 25 cc. of a stock solution of
approximately 0.2N iodine and making it up to 500 cc.
A ten cc. portion of 0.01N standard arsenious oxide was
titrated against the iodine solution in the manner Just des-
For all standardizations and titrations care was taken to
have all reagents at room temperature.
Ascorbic acid is rendered fairly stable in an acid medium
of proper pH value. Three per cent metaphosphorio acid has
been found very satisfactory for this purpose. Therefore, the
vegetables to bo analyzed were oollccted into metaphosphorio
acid of sufficient concentration to insure a three per cent
solution after the sample was mixed, and brought up to volume.
The day before samples were to be taken, 62,5 cc. of 12 per
cent metaphosphorio acid was put into clear glass bottles with
unlinod plastic lids. These bottles of acid were weighed, if
necessary for sample collection, and placed in the refrigerator
until they were used.
The samples were oollected at the college cafeteria as
described in the sampling procedure.
For the determination of ascorbic acid content, it was
neoessary to have the cellular structure of plant tissues well
broken down. For this purpose the Waring blendor was used.
To prevent excessive frothing, two to three drops of butyl
■tearate were added to the material before it was ground in
the blendor. The use of the Waring blendor for cooked pota-
toes resulted in a nonf llterable starch solution. The use of
a mortar and pestle for grinding proved satisfactory. Kahn
and Halllday (1944) reported that samples of cooked potatoes
macerated in a Waring blendor formed an "opaque gelatinous
After each sample was macerated and thoroughly mixed
either in the blendor, or in the case of potatoes, with mortar
and pestle, distilled water was added to the solution to make
up its volume to 250 co. It was mixed well, filtered, and
ten cc. aliquot portions were diluted with a small amount of
distilled water and titrated in duplicate with sodium
2,6-dlohlorophenollndophenol, A very faint pink whioh faded
within 30 seconds was considered the end point. Duplicate
titrations were always made for standardizations and for as-
corblo acid determinations. Oreater speed and greater preci-
sion were possible the second time. Prom the sundry titrations
calculations were made to determine the milligrams of ascorbic
acid per 100 grams of vegetable. The following formulas were
used in making the calculations:
The dye factor or rag. asoorblo acid per co. dye •
oo. As2 O3 x .00 x cc. lodlno against ascorbic acid
cc. iodine against Asg O3 x 00. dye against ascorbic acid
(1 cc, of Il/lOO iodine » .08 mg. ascorbio acid.)
The mg. ascorbic acid per 100 grams vegetable «
100 mrc. of vegetable x vol. of sol, x dye faotor x dye titration
wt. of vegetable used x vol. used for titration
DISCUSSION OF R2SU118
Experiments carried out on approximately 50 samples of
tomatoes taken over a period of five days Indicated th.'.t their
ascorbic acid values varied somewhat and that it was difficult
to ascribe these fluctuations entirely to any of the various
steps in preparation. The mean ascorbic acid content In 2£-
samples of ra?» tomatoes was 17.1 x 1.3 itig. per 100 grama.
This average corresponds to the lower values in the range of
15 to 40 mg. per 100 grams of most commercial varieties of
tomatoes as reported by Reynard and Kanapaux (1S42). It was
Impossible to find cut where and under what conditions the
tomatoes used In these experiments had been grown. Storage
and transportation problems were ^reat because of the war con-
ditions. It was evident, in so.ue cases, that the tomatoes had
been picked when very green. Moreover, they were not sorted
according to s^e, and they *ere not always well packed. The
fact that the ascorbic acid value of the tomatoes in this
study was not generally high added Interest to bba project.
Since tomatoes are usually included among the food3 that con-
tribute substantially to the vitamin C content of our diet,
it was of practical value to mates this investigation.
The range of 14.9 to 20.2 nig. per 100 grams did not show
as great variation In the raw tomatoes as might have been
expected because many workers have reported greater ranges
even in tomatoes of the same variety. In general samples of
cooked tomatoes seemed to indicate a decrease of tne original
asoorbic aold content but In the small troupe of samples
greatly varying results were obtained. In one set of three
samples there was apparently a 61 per cent retention of the
original ascorbic acid content when tomatoes were held at
room temperature after being washed, cored and baked for 22
minutes. Similar procedures seemed to result in a retention
of 94 per cent in another set of three samples. In two in-
stances cooked tomatoes appeared to have a greater asoorbic
acid content than did the raw tomatoes sampled on the same
day. These discrepancies oould have been due to the variable
content of ascorbio acid within the tomatoes. The samples of
raw tomatoes wore made up of quarters from four different
tomatoes but for sampling oooked tomatoes, whole tomatoes were
used. Thus a whole tomato of high original ascorbic acid con-
tent could have greater value even after being cooked than the
samples made up of parts of four raw tomatoes if these toma-
toes happened to be of lower original ascorbic acid content.
With one exception, the groups of small samples indicated that
the retention of ascorbio acid was decreased by an increased
Since steaming in the pressure steamer for five minutes
was the most typical method of oooklng tomatoes at the oafe-
ter-la, that method of oooklng was the one used in this ex-
periment when a larger number of samples were taken on the
same day. Composite samples were taken for testing both raw
and oooked tomatoes as described in the sampling procedure.
The mean ascorbic acid values found in the tomatoes were these:
raw, 16.4 i 0.5; steamed for five minutes, 14.1 t 2.4. Thus
the retention during cooking was approximately 87 per cent.
Holding the cooked tomatoes on the steam table for 15 minutes
caused no further decrease. This latter result Is In accord-
ance with the report of Gleim et al. (1946) In their study on
the effect of quantity preparation procedures on canned toma-
toes. They found that heating the canned tomatoes in a steamer
for 15 minutes caused "practically no destruction of ascorbic
Thfi ranr;e of the ascorbic acid content of raw shredded
cabbage per 100 grama for 25 samples was 35.2 to 54.2 m£.
Many investigators hove shown that the original ascorbic acid
content of cabbage may fluctuate greatly. In this study noth-
ing could be done to control the factors of variety, exposure
to sunlight during the growing period, and storage of the cab-
bage previous to purchase. Since the work was done In June
and the first part of Julv, 1945, summer cabbage was used.
However, It oould not be determined how much time had elapsed
since it was harvested, nor at what temperatures it had been
An average of 43.5 t 5.9 mg. per 100 "rams found in 25
samples of raw cabbage indicated a fairly high original ascor-
bic acid content.
Shredded cabbage was used for sampling as shreddinr was
typical of the manner of preparation for serving at the cafe-
teria and gave an opportunity to have the various parts of the
oabbage well mixed. Bray and Thorpe (1944) found an asoorbic
add range of 25 to 79 mg. per 100 grama In ten samples of
oabbage that had been out Into wedges, then oooked and strained.
They oonoluded that "ninoed or chopped" oabbage would give
better agreement between replicate samples.
Shredded cabbage held at room temperature for one hour
showed 94 to 96 per oent retentions of the original ascorbio
acid content of nine samples and 100 per oent retention in
the group of ten samples. There was only 88 per cent reten-
tion in one group of three samples. The loss in this case,
whloh might have been due to finer shredding, was greater
than the losses reported in the literature by recent workers.
In these experiments the shredding was done on a Hobart elec-
tric slloer. Ordinarily the cabbage was cut into shreds about
three-eighths of an inch wide.
Six samples of shredded cabbage held for 45 to 60 minutes
and steamed for seven minutes showed an asoorbic acid reten-
tion of 79 to 81 per cent of the original value. Ten samples
steamed for seven minutes Immediately after the cabbage was
shredded showed an average retention of 68 per cent.
The retention of ascorbio aoid during holding on the
steam table for 15 minutes was apparently less when the shred-
ded oabbage had been held from 45 to 60 minutes before being
put into the pressure steamer. Six samples of shredded cab-
bage held for 45 to 60 minutes, steamed seven minutes, and
held on the steam table for 15 minutes showed ascorbic acid
retentions of 66 to 74 per cent. Ten samples steamed seven
minutes and held 15 minutes on the steam table showed an
average retention of 85 per cent.
The potatoes usod In this study were of the Red Triumph
variety locally produced. Since the work was done about the
middle of July, it Is probable that the potatoes had been
recently harvested. The mean ascorbic acid value of 14 raw
samples 34.2 ± 3.1 rag. per 100 grams, on the basis of wet
weight, showed that the potatoes had a comparatively high
original ascorbic acid content. According to the report of
Leichsenrlng (1944) immature Irish Cobbler potatoes at the
Nebraska station had an ascorbic acid content of 36.8 mg. per
100 grams on June 30. The highest value given for Triumph
potatoes was 29.8 mg. in October. Values were not recorded
for this variety during June and July in the National Coopera-
tive Project. The range of 28.3 to 38.2 mg. per 100 grams
for the 14 samples of raw potatoes was not f-reater than was
expected because there were some variables that could cause
such results. The fluctuations could have been due to the
parts of the tubers tested. The samples were chosen from vari-
ous portions of the lot of potatoes being prepared for serving.
The potatoes cooked in a pressure steamer showed a reten-
tion of approximately 86 per cent. This was comparable to
some of the results reported in the literature. Mashing the
potatoes in the manner ordinarily done for serving resulted
in a retention of 55 per cent of the original ascorbic acid
content. The calculations made on the dry weight gave almost
the same results that were obtained on the wet basi3. It was
noticed thu»t some cooks subjected the mashed potatoes to longer
periods of mixing and whipping than others.
Holding the mashed potatoes on the back of the stove for
45 minutes resulted in an additional loss of ascorbic acid.
The average ascorbic acid value of potatoes tested immediately
after mashing was 19.6 t 1.3 mg. per 100 grams (wet basis) and
that of potatoes, mashed and held on the stove, was 14.7 x 1.1 mg.
Raw spinach is often served at the college cafeteria.
The washed, cut, raw spinach is placed in a stainless steel
bowl. A hot vinegar dressing is poured over the spinach which
is then held on the steam counter where it is served.
Since cooking destroys ascorbic acid to a greater or
lesser extent, there is an advantage in serving some vegetables
raw. However, the amount of this vitamin retained during the
preparation of vegetables to be served raw and during their
holding periods is subject to considerable variation.
An experiment was made to determine the results of holding
the cut spinach on the steam table for 15 minutes, and at room
temperature for one hour. No testa were made on the effect of
adding the dressing. The vinegar dressing Itself probably did
not cause a marked destruction of the ascorbic acid content of
the spinach although adding it when hot might have resulted in
some decrease. Quinn et al. (1946) found that adding a vinegar
mayonnaise to shredded oabbage aided the retention of ascorbic
acid. Similar results might be expected for spinach.
In this experiment the original ascorbic acid value of
the spinach was low. Of the first ten samples taken from the
unwashed, uncut spinach the mean value was 13.0 ± 1.2 mg. per
100 grama. This was lower than the mean of 15.0 * 2,4 mg.
found In the ten determinations of the washed, cut spinach.
The lower values in the unwashed, uncut spinach may have been
due to the greater quantity of stems which had not been re-
moved. According to Tressler, Hack, and King (1936) the ascor-
bic acid content of the stems of spinach is comparatively low.
The mean ascorbic acid value of the raw, washed, cut samples
was used for calculating percentage retentions because the
purpose of this experiment was to determine the effect of hold-
ing spinach on the steam table for 15 minutes and at roon tem-
perature for one hour. The variety of spinach and the length
of time since harvesting could not be determined. However,
the spinach showed marked deterioration, nearly half of the
amount purchased, one bushel, had to be discarded as the leaves
were badly wilted and slimy. According to the literature re-
ported, variety as well as storage time and temperatures are
very Important factors in the ascorbic acid content of spinach.
Holding the out spinach on the steam table for 15 minutes
gave a mean value of 12.3 i 1.9 mg. per 100 grams for ten sam-
ples. This was an 82 per cent retention of the original.
Holding the cut spinach at room temperature, 26.0° C, for one
hour gave a mean value of 10.8 i 1.7 lag. for ton samples. This
was a 72 per cent retention of the original and indicated a
very rnpld destruction. The loss might have bean due to the
fact that the spinach had been out Into small pieces. The
loss would probably have been retarded if the spinach had been
held uncut In the refrigerator and out as needed for serving.
The results obtained in these experiments carried out on
tomatoes, cabbage, potatoes, and spinach showed that these
vegetables as served in the cafeteria at Kansas State College
contained appreciable amounts of osoorblc acid. By a Judi-
cious choice of vegetables one could select at this cafeteria
a day's diet that would contribute an adequate amount of vita-
min C without including citrus fruit or juice in the menus.
Sarett et al. (194G) in roporting a study made on the
vitamin contont of restaurant foods found that "moot of the
cooked foods contained loss than ten mg. asoorblc acid per
100 grama" and that the daily ascorbic acid requirements could
be met only by the inoluslon in the diet of fresh fruit Juices.
Certainly ascorbio acid is extremely labile and great oare
should be taken to oonserve the amounts that may be present in
In this study investigations were made to determine the
effects of oertain preparations and serving techniques on the
ascorbic acid content of selected vegetables at the cafeteria
of Kansas State College.
Experiments were carried out on tomatoes, cabbage, pota-
toes, and spinach*
The results indioated that the ascorbic acid oontent of
tomatoes is somewhat decreased by cooking. Steaming in the
pressure steamer for five minutes resulted in an 87 per cent
retention of the orijinal ascorbic acid content of tomatoes.
Holding oooked tomatoes on the steam table for 15 minutes
caused no further loss in their ascorbic acid values.
Shredded cabbage held at room temperature for one hour
retained, in most of the samples studied, from 94 to 100 per
cent of its original ascorblo acid content. Cabbage steamed
for seven minutes showed 79 to 88 per cent retentions of as-
corbic acid. Holding cooked cabbage on the steam table for
15 minutes caused a slight decrease in its ascorbic acid value.
The retention of the ascorbic acid in potatoes during
oooking was about 86 per cent. Mashed potatoes showed a 55
per cent retention of their original ascorbic acid oontent.
Holding masliod potatoes on the back of the stove for 45 min-
utes caused a considerable decrease.
Haw spinach held on tho steam table for 15 minutes gave
an ascorbic add retention of 82 per cent. Cut spinach held
at room temperature lost its ascorbic acid rapidly.
The data indicated that during June and July of 1945 the
ranges of asoorblo aold values In 100-gram amounts of some
vegetables were as follows:
Tomatoes, raw 14.9 - 20.2 mg.
■ steamed 12.8 - 15.7 "
" held on steam table 15 minutes . 11.7 - 17.9 "
Cabbage, raw 55.2 - 54.2
" steamed. 34.4 - 39.0 "
" held on steam table 15 minutes . 33.0 - 30.1 "
Potatoes, raw 2P.3 - 30.2 "
mashed 17.7 - 21.7 ■
" " held on stove 45 minutes. . 13.2 - 17.1 "
Spinach, raw 10.9 - 18.7 "
n held on steam table 15 minutes. . 8.0 - 14.4 "
" " at room temperature 60 minutes 8.5 - 12.6 "
The findings in this study showed that commendable proce-
dures were used in the preparation and serving of these vege-
tables at the college cafeteria.
Sincere appreciation is hereby expressed to Reverend
Mother Thomas whoso encouragement prompted the undertaking
of this work and to Rovorond Mother Cecilia and the Ursullne
Sisters of Paola, Kansas, who made its completion possible.
Deep gratitude is also due to Dr. Leah Asoham whose
direction and guidance have been Invaluable and to Miss Mary
Smull for her gracious oooperation in the cafeteria project.
Bessey, 0. A.
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Bray, H. G. and W. V. Thorpe.
Sampling of cooked cabbage in nutrition surveys. Nature.
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Brown, A. P. and F, Moser.
Vitamin C content of tomatoes. Pood Res. 6:45-55. 1941.
Burrell, R. C., H. D. Brown, and V. R. Ebrlght.
Ascorbic acid content of cabbage as influenced by variety,
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Currence, T. II.
Comparison of tomato varieties for vitamin C content.
Amer. Soc. Hort. Scl. Proc. 37:901-904. 1940.
Curlar, K. L. , J. B. Jones, K. W. Harris, and P. Penton.
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Dove, W. P., E. P. Murphy, and R. V. Akeley.
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Dunker, C. and C. Fellers.
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Esselen, V« B., M. E. Lyons, and C. P.. Fellers.
The composition and nutritive value of potatoes with special
emphasis on vitamin C. Mas. Agr. Expt. Sta. Bui, 390.
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22:29-31. Jan. 1946.
Gould, S,, D. K. Tressler, and C. G. King.
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Halllday, E. f and I. Noble.
Recent research In foods. Jour. Home Econ. 20:15-21. 1936.
Hallswork, E. 0. and V. M. Lewis.
Vurlation of ascorbic acid in tomatoes. Nature. 154:431-432.
Hamner, K. C., l. Bernstein, and L. A. Maynard.
The effects of light intensity, day length, temperature, and
other environmental factors on ascorbic acid content of toma-
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Higglns, Miriam JSason.
The retention of ascorbic acid in institution and in home-
cooked vegetables. Unpublished thesis. Univ. of Chicairo.
46 p. 1342. "
Hlnaon, W. P., k. k. Brush, and E. G. Halllday.
The nutritive value of canned foods: VI. Effect of large
scale preparation for serving on the uscorbio acid, thiamin,
riboflavin content of commercially-canned vegetables. Jour.
Amer. Dietet. Assoc. 20:752-760. Dec. 1944.
Ijdo, J. B. h.
Vitamin C content of different species of potatoes. Nutr.
Abs. and Rev. 7:612. 1937.
Ireeon, M. 0. and M. S. Eheart.
Ascorbic acid losses in cooked vegetables. Jour. Home Econ.
Isgur, B. and C. Fellers.
A preliminary study of the relationship between vitamin C
content and increased growth resulting frca fertilizer
applications. U. S. D. A. Expt. Sta. Record. 78:483.
Jenkins, Q. N.
Ascorbic acid in mashed potatoes. Nature. 151:473. 1943.
The potato as a source of vitamin C. Nutr. Abs. and Rev.
21C4. Jan. 1944.
Kahn, R. K. and E. G. Halllday.
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cooking and standing on the steam table. Jour-. Amer. Dietet.
Assoc. 20:220. April 1944.
Lsmpitt, L. H., L. C. Baker, and T. L. Parkinson.
Disappearance of the ascorbic acid In raw cabbage after
mlnolng or chopping. Nature. 149:697-698. 1942.
Factors affecting the nutritive value of potatoes. Progress
Note, National Cooperative Project, North Central Region.
Minn. Agr. Expt. Sta. 1944.
Hack, G. L. and D. K. Tressler.
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Tillman's method for the determination of ascorbic acid.
Jour. Biol. Chem. 118s735-742. 1937.
Mayfield, H. L. and J. E. Richardson.
The effect of winter storage on the vitamin content of
cabbage and onions. Mont. Agr. Expt. Sta. Bui, 379.
McCay, C. M., M, Pijoan, and H. R. Taubken.
Ascorbic acid losses in mincing fresh vegetables. Science.
99:454-455. June 2, 1944.
Murphy, E. P.
The ascorbic acid content of different varieties of Maine-
grown tomatoes and cabbage as influenced by locality,
season, and stage of maturity. Jour. Agr. Res. 64:483-503.
Noble, I. and E. Waddell.
The effects of different methods of cooking on the ascor-
bic acid content of cabbage. Pood Res. 10:246-254.
Hoy- June 1945 .
Noble, I. and E. Waddell.
The retention of ascorbic acid In cabbage during cooking
by different methods. Progress Notes, National Cooperative
Project, Conservation of the Nutritive Value of Poods.
Paper No. 546 misc. series, Minn. Agr. Expt. Sta. 1946.
Phillips, M., N. Dickerson, and P. Penton.
The ascorbic acid, thiamin, and riboflavin retention in
fresh market, home frozen, and commercially dehydrated
spinach, cooked by several methods. Progress Notes,
National Cooperative Project, Conservation of the Nutri-
tive Value of Poods. N. X. Agr. Expt. Sta. (Date was not
Platenius, H. and J. Jones.
The effect of modified atmosphere storage on the ascorbic
acid content of some vegetables. Pood Res. 9:378-385.
Procter, B. and D. Oreenlle.
The determination of optimum conditions for domestic
refrigeration of foods. Pood Res. 3:199-203. 1938.
The effect of shredding and grating on the vitamin C
content of raw vegetables. Nature. 149-49S. Hay 1942.
Qulnn, P. V., F. I. Sooular, and M. L. Johnson.
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U. a« D. A. Sxpt. St. Pecord. 74:886-887. 1936.
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